1. Field of the Invention
The present invention relates to a dual-membered suctional gasket with a reliable gastighness attained by a dual-structure having a sealing function comprising an inner member and an outer member, and the gasket is applicable to various purposes.
2. Brief Description of the Related Art
Such gaskets having merely dual-membered sealing portions constituted by inner members and outer members have been known (see for example, Japanese laid open utility model No. 2-127859 and Japanese laid open patent No. 10-259875).
In some case, elasticity of whole walls of sealing portions in a gasket is reduced to a quite low level in order to enhance a sealing performance of the gasket (see Japanese laid open patent No. 8-13594).
Further, in some case, a gasket having measures to prevent the gasket from falling off and falling down has been also known (see Japanese laid open patent No. 2003-172453).
The dual-membered gaskets in the above-cited references are basically constituted by inner, outer sealing members and solid connecting members for connecting the inner and outer sealing members together, and are attached to objects to be sealed by fitting the gaskets to recessed portions of the objects. The above-cited references only disclose that inner and outer sealing members can prevent the gaskets from falling off or falling down and show suction effects. However, the gaskets disclosed in these cited references do not sufficiently attain fitting reliabilities of the gaskets to the objects to be sealed, performances of the suction effects and reliable air venting operations.